<!DOCTYPE html>
<html lang="ch-CN">
<head>
    <meta charset="UTF-8">
    <title>BFC_解决塌陷</title>
</head>
<style>
  *{
    margin: 0;
    padding: 0;
  }
.outer{
  width: 100%;
  height: auto;
  background-color: #888888;
  /*display: inline-block;*/
  /*position: fixed;*/
}
.inner{
  width: 200px;
  height: 200px;
  background-color: black;
  margin: 50px;
}
</style>
<body>
    <div class="outer">
      <div class="inner"></div>
      <div class="inner"></div>
      <div class="inner"></div>
    </div>
</body>
</html>